An overview on the properties and applications of polymer and inorganic planar 1D photonic crystals fabricated from solution is provided here. In the last decades, photonic crystals became technologically relevant for light management, photovoltaics, sensing, and lasing. Such structures are traditionally produced by lithographic and vacuum techniques, but the need to reduce costs and to scale‐up the fabrication have lead the research toward new materials, simplified structures, and low‐cost mass scale growth processes. In this regard, polymer and inorganic mesoporous distributed Bragg reflectors fabricated from solution attracted considerable technological interest. This review focuses on the properties of such structures, concentrating on state‐of‐the‐art fabrication and applications.

The lack of sensors for low cost, extensive, and continuous detection of vapor pollutants is a serious concern for health and safety in industrialized urban areas. Colorimetric sensors, such as distributed Bragg reflectors made of polymers, could achieve this task thanks to their low cost and easy signal transduction but are typically affected by low vapor permeability and lack of selectivity without chemical labeling. Here we demonstrate all-polymer Bragg multilayers for label-free selective detection of organic volatile compounds. The system exploits the ability of amorphous poly(p-phenylene oxide), PPO, to uptake large amount of guest molecules and to form cocrystalline phases with distinct optical properties. Bragg stacks embedding PPO active layers show selective colorimetric response to vapors of carbon tetrachloride and aromatic homologues, which can be revealed by the naked eye.

A theoretical approach for the interpretation of reflectance spectra of opal photonic crystals with fcc structure and (111) surface orientation is presented. It is based on the calculation of photonic bands and density of states corresponding to a specified angle of incidence in air. The results yield a clear distinction between diffraction in the direction of light propagation by (111) family planes (leading to the formation of a stop band) and diffraction in other directions by higher-order planes (corresponding to the excitation of photonic modes in the crystal). Reflectance measurements on artificial opals made of self-assembled polystyrene spheres are analyzed according to the theoretical scheme and give evidence of diffraction by higher-order crystalline planes in the photonic structure.